本文关键词：复合型半导体纳米光催化剂的设计、制备及催化性能研究 出处：《内蒙古大学》2017年博士论文 论文类型：学位论文
更多相关文章： 绿色合成 钽基光催化剂 铋基光催化剂 氮化碳基光催化剂 可见光催化 选择性催化
【摘要】：太阳能作为一种新兴可再生能源,在化石燃料日趋减少的情况下已经成为人类使用能源的重要组成部分。而自然界中太阳能的转化主要通过植物的光合作用来完成。通常需要数月至数百万年才能参与到人类的生产生活中。自20世纪70年代,Fujishima和他的同事在《Nature》上发表题为 " Electrochemical photolysis of water at a semiconductor electrode"论文,报道了 TiO2的光电催化解水反应,首次提出"光催化"这一概念。光催化技术的出现有望加快或部分跳过上述能量转化过程,现已应用到许多有前景的领域,例如,光解水制氢解决能源问题,光催化降解净化污染物解决环境问题,通过光催化有机合成直接参与工业生产。开发性能优良的光催化体系是光催化技术解决能源环境问题的关键。本论文以开发高性能可见光催化剂为目的,通过结构组成调控、贵金属负载、材料复合等方法优化催化活性。深入探讨了半导体光催化体系的催化性能、反应机理以及应用前景,研究内容如下:(1)设计制备了短程有序型NaxTaOy · nH2O光催化剂,实现了可见光下高效地催化苯甲醇选择性需氧氧化为苯甲醛。同步辐射X射线广角散射和透射电子显微镜证明短程有序型NaxTaOy · nH2O的短程有序度与缺陷化学特征可以被很好的调控。短程有序结构为NaxTaOy·nH2O提供了大量的缺陷中心和较大的比表面积,是实现大范围可见光响应和光催化苯甲醇选择性需氧氧化的关键因素。本研究为设计开发缺陷可控的短程有序催化体系及有效催化苯甲醇需氧氧化反应提供了新颖的策略。(2)设计制备了 Sn2Ta2O7@SnO2复合材料。结合XRD,TEM,SEM系统性的研究了 Sn2Ta2O7@SnO2核壳结构的形成过程和p-n异质结的构造。通过XPS与穆斯堡尔谱研究发现,Sn2+与Sn4+的原位氧化还原反应可以实现SnO2与Sn2Ta2O7的自掺杂,实现可见光的响应。同时SnO2与Sn2Ta2O7匹配的能带结构能够抑制电子与空穴的复合,实现光催化活性的提升合有机污染物的高效降解(可见光下20分钟内降解98%的MO)。研究了复合材料的电荷分离过程并对催化机理进行了深入的讨论。研究成果对于通过复合宽带隙半导体开发兼具高催化活性与可见光响应能力的新型催化体系具有重要意义。(3)通过将ZnFe2O4均匀的包覆在Bi球的表面构筑Bi@ZnFe2O4复合材料。该催化体系可以实现对硝基苯酚选择性还原为对氨基苯酚,在25分钟内转化率达98%。可见光的照射可以大幅提高催化活性。此外,Bi@ZnFe2O4催化剂表现出极为优秀的稳定性与循环使用能力,在循环使用10次之后催化性能仍然没有损失。研究发现基于ZnFe2O4与Bi之间界面处的强氧化还原反应产生大量Bi3+离子以及二者之间形成的肖特基势垒可有效实现分离光生电子空穴对,促进了光协同催化作用。此外,壳层设计为磁性分离以及催化剂的循环使用提供了便利条件。本研究有可能实现以经济的Bi元素代替贵金属用于环境友好的催化氢化硝基苯类化合物的可能性。(4)设计了资源丰富的锌铁与铋构成的光催化体系,用于CO2选择性还原为高能燃料,该反应中ZnFe2O4充当可见光收集器,后过渡金属Bi纳米微球充当电子储存器并提供反应活性位点,实现由CO2向CO的选择性转化。通过瞬态红外光谱研究发现,光生电子由ZnFe2O4的导带快速的向Bi上迁移,因此可实现高效的空间电荷分离效率。通过精确地调控Bi@ZnFe2O4材料的化学组成、表面结构,在可见光(λ≥420nm)照射下的CO转化速率可以达到40.2μmol·g-1·h-1。深入研究了反应机理,提出Bi3+/Bi0氧化还原电对对光催化剂选择性还原CO2起到了决定性的作用。(5)设计构造金属-半导体型肖特基异质结Pd/g-C3N4催化体系,用于光催化铃木偶联反应。通过将Pd负载在g-C3N4上可以实现光照下电子由g-C3N4向Pd的转移,同时在g-C3N4产生具有氧化能力的空穴。在光催化铃木偶联的过程中,电子与空穴起到了不同的作用。Pd上富集的电子可以切断卤代苯上的C-X键,而g-C3N4价带上的空穴可以破坏苯硼酸中的C-B键实现两种反应物的同步活化。在可见光照射下Pd/g-C3N4对于碘苯与苯硼酸偶联反应的TOF可达117h-1,转化率高达99%。本研究为联苯类化合物的绿色光催化合成提供了合理的途径,同时也为设计用于有机物转化反应的新型可见光催化剂提供了一种有效的策略。(6)通过光沉积的方法制备CsTaWO6/Au,随后与g-C3N4结合构造了一种新颖的三相复合材料CsTaWO6/Au/g-C3N4。较小的Au粒子均匀的分布于CsTaWO6与g-C3N4之间,由于优良的光吸收能力与电子空穴对分离效率实现了增强的光解水制氢活性。与g-C3N4,Au/CsTaWO6,CsTaWO6,Au/g-C3N4 相比 CsTaWO6/Au/g-C3N4 显示出了显著优异的催化活性。机理研究证明体系中的Au在传递电子方面起到了重要的作用。本研究为构造高性能三元光催化剂提供了一种可能的途径。
[Abstract]:Solar energy as a new renewable energy, in the case of dwindling fossil fuel has become an important part of human use of energy. And the transformation in nature of solar energy through photosynthesis in plants. Usually used to complete the required number of months to millions of years to participate in the production of human life. Since 1970s, Fujishima and his colleagues at
entitled "Electrochemical photolysis of water at a semiconductor electrode" paper, reported the photoelectrocatalytic TiO2 water reaction solution, put forward the concept of "photocatalytic" appeared for the first time. The photocatalytic technology is expected to accelerate the skip or part of the energy conversion process, has been applied to many promising areas, for example water photolysis, solve the energy problem, the photocatalytic degradation of pollutants to solve environmental problems, through the photocatalytic organic synthesis directly. With the development of industrial production. The photocatalytic system with excellent performance is the key of photocatalytic technology to solve energy and environmental issues. In order to develop the high performance of visible light catalyst for the purpose of the structure regulation, noble metal loading, optimization of catalytic activity of composite materials. The method deeply investigates the catalytic performance of semiconductor photocatalysis reaction system. The mechanism and the application prospect and research contents are as follows: (1) NaxTaOy - type short-range ordered nH2O photocatalyst was prepared, can effectively catalyze benzene methanol selective aerobic oxidation under visible light to benzaldehyde. Synchrotron radiation X ray wide-angle scattering and transmission electron microscopy demonstrated NaxTaOy nH2O short-range order of the short-range order the chemical characteristics and defects can be easily controlled. Provides a large number of defect centers and large surface area of short-range order structure for the NaxTaOy nH2O, is to achieve a wide range The visible light response and the key factors of the photocatalytic benzene methanol selective aerobic oxidation. This study for short-range ordered catalytic system design defects of controllable and effective catalytic aerobic oxidation of benzyl alcohol provides a novel strategy. (2) Sn2Ta2O7@SnO2 composites were prepared. The combination of XRD, TEM, SEM of the system research Sn2Ta2O7@SnO2 core-shell structure forming process and p-n heterojunction structure. Found by XPS and Mossbauer spectroscopy, Sn2+ and Sn4+ in situ oxidation reduction reaction can achieve self doping of SnO2 and Sn2Ta2O7, in response to visible light. At the same time, Sn2Ta2O7 and SnO2 compound can inhibit electron and hole structure, efficient the photocatalytic activity of degradation of organic pollutants increase (MO 20 minutes 98% degradation under visible light). The charge separation process of composite materials and the catalytic mechanism of the deep In the discussion. The research results have important significance for new catalysts with high catalytic activity and ability of visible light response by compound wide band gap semiconductor development. (3) the surface of ZnFe2O4 coated on Bi ball build Bi@ZnFe2O4 composite material. The catalytic system can be realized by selective reduction of p-nitrophenol to p-aminophenol in 25 minutes, the conversion rate of 98%. visible light irradiation can significantly enhance the catalytic activity. In addition, the Bi@ZnFe2O4 catalyst showed very good stability and recycling ability, after recycling 10 times the catalytic performance is still no loss. Based on the Schottky barrier formed between the strong oxidation at the interface between ZnFe2O4 and Bi reduction reaction a large amount of Bi3+ ions and the two can effectively realize the separation of photogenerated electron hole pairs found that promoted light catalysis. In addition, shell. For magnetic separation and catalyst recycling facilities provided. This research is likely to replace the noble metal elements Bi the economic possibilities for environmentally friendly catalytic hydrogenation of nitrobenzene compounds. (4) the design of zinc with bismuth rich composition photocatalytic system for selective reduction of CO2 for high energy fuel ZnFe2O4, the reaction as a visible light collector, transition metal Bi nanoparticles as electronic storage and provide reactive sites, realizing the transformation from CO2 to CO. Through the study of selective transient infrared spectroscopy showed that the photogenerated electrons from the conduction band of ZnFe2O4 fast to Bi migration, so as to realize the efficient space charge separation efficiency the precise regulation of Bi@ZnFe2O4. The chemical composition of material, surface structure, in the visible light (lambda = 420nm) under the irradiation of the CO conversion rate can reach 40.2 mol - g-1 - h-1. In-depth study of the reaction mechanism, the redox reactions of Bi3+/Bi0 CO2 plays a decisive role in the reduction of catalyst selectivity. (5) the design structure of metal semiconductor Schottky heterojunction Pd/g-C3N4 catalyst for photocatalytic reaction. The SUZUKI Pd load in g-C3N4 can be realized by electronic transfer under illumination g-C3N4 to Pd, and has the ability of oxidation hole generated in g-C3N4. In the process of photocatalytic SUZUKI coupling, electron and hole plays the role of.Pd on different concentration of electrons can cut the C-X button on the halobenzene, activation of g-C3N4 valence band holes can be destroyed in the implementation of C-B key phenylboronic acid two kinds of reactants simultaneously. Under visible light irradiation for Pd/g-C3N4 coupling of iodobenzene with phenylboronic acid TOF is 117h-1, the conversion rate as high as a green light for catalytic synthesis of biphenyl compounds 99%. this study For a reasonable way, but also provides an effective strategy for the design for the new photocatalyst organic conversion reaction. (6) the preparation of CsTaWO6/Au by optical deposition system, then combine with g-C3N4 to construct Au particles distribution of a novel three-phase composite material CsTaWO6/Au/ g-C3N4. small uniform in between CsTaWO6 and g-C3N4, due to the excellent light absorption ability and electron hole separation efficiency achieved enhanced water photolysis activity. With g-C3N4, Au/CsTaWO6, CsTaWO6, Au/g-C3N4 compared with CsTaWO6/Au/g-C3N4 showed excellent catalytic activity significantly. Research on the mechanism of proof system of Au in electron transfer plays an important role. The research provides a possible way to construct high performance three yuan light catalyst.
【学位授予单位】：内蒙古大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36
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本文编号：1429487
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